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Table of Contents - June 2012 - Volume 6, Issue 06  

Physiology and functional biology of systems

Effect of prepartum somatotropin injection in late-pregnant Holstein heifers on metabolism, milk production and postpartum resumption of ovulation

A. Schneidera1a2 c1, E. Schweglera1a2, P. Montagnera1a2, L. T. Haxa1a2, E. Schmitta1a2, L. F. M. Pfeifera2a3, F. A. B. Del Pinoa2a4, I. Bianchia2a5, G. R. Paludoa6 and M. N. Corrêaa1a2

a1 Department of Veterinary Clinics, Veterinary College, Federal University of Pelotas, Campus Universitário, CEP 96010-900 Pelotas, RS, Brazil

a2 Núcleo de Pesquisa, Ensino e Extensão em Pecuária (NUPEEC), Veterinary College, Federal University of Pelotas, Campus Universitário, CEP 96010-900 Pelotas, RS, Brazil

a3 Animal Reproduction Laboratory, EMBRAPA CPAFRO, BR 364 – Km 5, 5, CEP 76815-800 Porto Velho, RO, Brazil

a4 Department of Biochemistry, Federal University of Pelotas, Campus Universitário, CEP 96010-900, Pelotas, RS, Brazil

a5 Department of Pathology, Veterinary College, Federal University of Pelotas, Campus Universitário, CEP 96010-900, Pelotas, RS, Brazil

a6 Department of Pathology, Veterinary College, University of Brasília, Campus Universitário Darcy Ribeiro, Asa Norte, CEP 70910-970, Brasília, DF, Brazil

Abstract

The aim of this study was to determine the effect of prepartum somatotropin injection in late-pregnant Holstein heifers on metabolism, milk production and resumption of postpartum ovulation. For this study, 31 late-pregnant Holstein heifers were used. The heifers were assigned randomly into two treatments: (1) 500 mg sc injections of somatotropin (somatotropin treatment, n = 15) at −35 and −21 days, and, if pertinent, at −7 days from expected calving date and (2) no treatment (control group, n = 16). Blood samples were collected weekly from −5 to 7 weeks after calving. Heifers with progesterone concentrations in plasma above 1 ng/ml in two consecutive postpartum samples were considered as having resumed ovarian activity. A higher proportion (P = 0.04) of heifers treated with somatotropin resumed ovarian activity in the first 7 weeks post partum (73.3%; 11/15) compared with the control group (37.5%; 6/16). A higher number (P = 0.02) of heifers in the somatotropin treatment group also ovulated during the first postpartum follicular wave (53.3%; 8/15) compared with the control group (12.5%; 2/16), as indicated by the number of heifers ovulating in the first 3 weeks post partum. Pregnancy rate was not affected by treatments (P > 0.10) and averaged 40.0% (6/15) in somatotropin-treated and 25.0% (4/16) in control heifers when evaluated up to 150 days in milk. Somatotropin treatment increased the average daily milk production by 2.8 kg/cow per day (P < 0.0001) and reduced the somatic cell count (P = 0.009). Plasma IGF-I was higher (P < 0.05) for somatotropin-treated heifers in the prepartum period. Insulin and body condition score were higher (P < 0.05) and non-esterified fatty acids were lower (P < 0.05) for somatotropin-treated cows in the early postpartum period. In conclusion, somatotropin injection during the prepartum period in late-pregnant Holstein heifers was able to increase the proportion of heifers resuming ovarian activity early post partum, inspite of higher milk production.

(Received April 28 2011)

(Accepted October 28 2011)

(Online publication November 28 2011)

Keywords

Correspondence:

c1 E-mail: augusto.schneider@live.com